Core magnetization device



Filed Sept 19, 1962 FIG. 4

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INVENTOR C. B. VOGEL BYJWJM HIS ATTORNEY United States Patent O 3,183,983 CORE MAGNETIZATION DEVICE Charles B. Vogel, Houston, Tex., assigner to Shell @il Company, New York, N.Y., a corporation of Delaware Filed Sept. 19, 1962, Ser. No. 224,673 1 Claim. (Cl. 175--44) This invention pertains to drilling operations and more particularly to core drilling devices used to obtain cores during the drilling of boreholes.

In the drilling of oil wells particularly exploratory Wells, it is desirable to obtain cores from the various formations that are penetrated by the borehole. In order to obtain cores' various core drilling devices have been developed. These devices consist of a circular drill bit for removing a core that is retained in a core barrel disposed in the interior of the drill bit. While these devices are satisfactory for removing cores from formations penetrated by a borehole, the devices used for marking the sections of the core have been unsatisfactory.

Prior marking devices have consisted of means for marking in a known direction the end of the core before it is drilled. While marking of the end of the core is satisfactory providing the core does not break during drilling operation, it is unsatisfactory where the core breaks. Normally, the core breaks in numerous short sections and at times it is possible to orient various sections of the core by matching the breaks between individual pieces. Many times it is impossible to orient the individual sections of the core by matching the breaks in the separate pieces. When this occurs except for the initial sections of the core, the remainder of the core is not completely satisfactory since it is impossible to orient the core geographically with the formation from which it was removed.

Accordingly, it is the principal object of this invention to provide a novel device for continuously marking the total length of the core in order that the individual sections rnay be oriented with respect to each other and with respect to the formation.

It is a further object of this invention to provide a unique device for continuously placing a correlatable mark on sections of the core as they are removed or cut from a formation, with the device in addition orienting these marks with respect to the direction of the magnetic north.

A still Ifurther object of this invention is to provide a means for continuously marking a core in which the direction of the magnetic north is marked on a core as it is removed from the formation.

The above objects and advantages of this invention are obtained by providing means for placing a continuous mark on the core and marking the direction of magnetic north on the core throughout its entire length. The term marking a core as used in the following description refers to the magnetizing of a core along an axis perpendicular to the longitudinal axis of the core. The axis of magnetization in addition bears a known relation to magnetic north. The means utilized may consist of a large ring magnet that is provided with a means that permits the magnet to orient with the magnetic north. The permanent magnetism in the magnet then marks a north-south direction of the core as it is removed from the formation. A second means utilizes a compass coil that detects the direction of magnetic north and then actuates an electronic circuit to pulse coils that are disposed to mark the magnetic north direction on the core as it is removed from the formation.

The above objects and advantages of this invention will be more easily understood from the following deice tailed description of a preferred embodiment when taken in conjunction with the attached drawings in which:

FIGURE 1 is a vertical section of a core drill utilizing the marking device of this invention for marking the core;

FIGURE 2 is a second vertical section of a core drill showing a second embodiment of the marking device of this invention;

FIGURE 3 is a block diagram of the electronic circuitry utilized in the embodiment shown in FIGURE 2; and

FIGURE 4 is a horizontal section taken along line 4 4 of FIGURE l.

Referring now to FIGURES l and 4, there is shown a core drilling arrangement of conventional construction. The core drill consists of a circular drill bit 10 that is provided with a cutting surface 11 on its lower end. As the drill bit 1@ rotates it will cut or remove a section of the formation 12. The drill bit 10 is connected to a stub tube or drill string section 13 which in turn is coupled to the drill string not shown in FIGURE 1. The core or section of formation 12 is retained in a core barrel 14 that,l is provided with inwardly projecting sections 15 to grip the core section. The core barrel 14 is rotatably supported at its upper end by mean-s of a radial thrust bearing 17 that is secured to the end of the core barrel by retaining ring 16. The thrust bearing is similarly retained in the stub tube section 13. This type of core drill and core ba-rrel is well known and thus further construction details are deemed unnecessary.

The marking means of this invention is disposed around the modified lower end of the core barrel 14 and consists of an annular chamber Ztl that is attached to the outer surface of the core barrel by suitable means such as welding. Disposed Within the chamber 20 is a ring shaped magnetic member 21. The magnetic member 21 is magnetized in a diametrical direction in much the same manner as a compass magnet would be magnetized. The magnetic member 21 is supported in a suitable fluid Z2, for example, the uid may be mercury that would easily support a magnetic member formed of iron or similar material. The fluid 22 serves to freely support the magnetic member Z1 to permit the member to align its magnetic axis with the magnetic north-south direction of the formation. In addition to a uid support, other means of support may also be used, for example the magnetic member Z1 could be mounted on anti-friction bearings as, for example ball bearings, or the like.

In addition to the above requirements for the magnetic member 21 it is preferable to form the members adjacent the magnetic member 21 out of non-magnetic material. For example, the drill bit 1t) and the core barrel 14 could be formed of non-magnetic stainless steel or similar alloys. When the coring drill is operated it will cut the section of formation 12 and as the section of formation passes upwardly into the core barrel 14 it will be magnetically marked along the north-south magnetic axis of the earth by means of the magnetic member 21. In order to provide a sufficient marking on the core the magnetic member 21 must have a relatively large permanent magnetism. After the core is removed from the earth the north-south direction on the core can easily be determined by means of various laboratory instruments. Knowing the north-south direction of the core it will be a simple matter to orient the core within the formation.

As seen from the above description, a simple means has been provided for continuously marking the core as it is removed from the earth. The marking will continue even though the core breaks and the new sections are not aligned with the old sections. Thus, it will be a simple matter to align the various core sections even though the distinguishing marks between individual sec- Y il tions of the core are completely removed. Furthermore, if one desires only to place a continuous co-rrelatable mark on the core pieces for aligning the pieces with respect to the other, then the marking magnet may be locked in a xed position in the core barrel.

Referring noW to FIGURE 2, there is shown a second embodiment of this invention that utilizes electrical means for the magnetic means to continuously mark a north-south magnetic diameter on the core. In FIG- URE 2, elements that are Ithe same as those in FIGURE 1 bear similar numbers. The core drilling bit lil and the core barrel 14 are substantially the same as those shown in FIGURE 1 and will not be described further. Disposed in a recess 30 formed in the wall of the stub tube section 13 is a pick-up or compass coil 3l. The compass coil generates a signal as its eiliective axis becomes aligned with the direction of the magnetic iield of the earth. The signal from the compass coil is utilized in an electronic circuit 32 to generate a suitable pulse that is supplied to tWomarking coils 33 and 34 having cores 33 and 34. The marking coils are aligned with the compass coil 31 and the cores 33 and 34 of the marking coils serve to generate a magnetic field to magnetically mark the core in the north-south direction.

Referring now to FIGURE 3, there is shown the electronic ci-rcuit 32. The compass coil 3l is coupled to an amplifying circuit 40 that in turn is coupled to trigger circuit 41. The output of the trigger circuit is coupled to the two marking coils 33 and 34 in series. A power supply 42 is coupled to both the amplifier and trigger circuit, with the power supply being preferably battery operated to eliminate the need for any cables connecting the marking device to the surface. The trigger circuit 4l. should supply a large amplitude short duration pulse whenever the compass coil 31 generates a signal of the proper polarity. This large amplitude pulse when supplied to the marking coils 33 and 34 will generate a magnetic field of suflicient size to magnetically mark the core being removed by the core bit 1t?. A suitable circuit for use as a trigger circuit would be a monostable multivibrator that is triggered to its unstable condition by a pulse of the proper polarity and amplitude. Such a multivibrator can be adjusted so that it triggers on a particular pulse that for convenience can be chosen to be the pulse that occurs when the compass coil 31 passes the north axis of the earths magnetic field.

The embodiment shown in FIGURES 2 and 3 will supply a plurality of individual pulses, one for each lrotation of the drill bit. These pulses will be sutlicient to mark substantially the full length of the core removed by the core bit l0. Accordingly, it is seen that the embodiment of FIGURES 2 and 3 provides a means for continuously marking the core as it is removed. Thus the core will be marked even if -it breaks during or subsequent to its removal. The markings on the core from the embodiment of FIGURES 2 and 3 can then be used to orient the core with the formation. Furthermore, with this second embodiment, the stationary core barrel may be omitted from the coring device if desired.

l claim as my invention:

Core marking device for core drilling system comprising:

a core drilling system having a drill string with a rotatable core barrel therein and a drill bit, said core drilling system being disposed at the lower end of said drill string;

a pick-up coil disposed on said drill string adjacent the outer surface of the core barrel;

a power supply;

a trigger circuit, said trigger circuit being coupled to said power supply and said pick-up coil being coupled to the input side of said trigger circuit;

a pair of diametrically opposed coils having core-s therein and disposed on the drill string adjacent the outer surface of the core barrel with their axes aligned with the axis of the pick-up coil, said coils being coupled to the output side of said trigger circuit to magnetize the core as the core is cut by said core drilling system.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDE'IT, Examiner. 

